1. Field of the Invention
This invention relates to apparatus and methods for storing data, and more particularly to apparatus and methods for storing data on arrays of powered-down storage devices.
2. Background of the Invention
The emergence of the Internet and the growth of business enterprises have resulted in a dramatic increase in server-centric applications. This increase has caused an equally dramatic rise in data-centric services, such as transaction processing systems, web portals, email servers, stock trading and financial transaction systems, search engines, file servers, and the like. No longer just the domain of larger corporations, such data-centric services are becoming more prevalent with smaller business enterprises and institutions. These data-centric services are increasingly important in the global economy as millions (and perhaps even billions) of users rely on these services each day.
One thing that each of the above data-centric services has in common is that each typically relies heavily on storage systems for their data storage and processing requirements. Often, these storage systems are implemented as arrays of disk drives, tape libraries, or other storage devices. These storage systems may, in turn, be connected to networks to form storage-area-networks or network-attached storage. As data-centric services increase, reliance on storage systems of various types also increases.
Unfortunately, as reliance on storage systems continues to increase, the power consumed by the storage systems also increases. The increased power consumption can significantly increase running costs, stresses on power supplies, impacts on the environment, and device failure rates. These power costs are eventually passed on to consumers. Another side-effect of high power consumption is heat generation. As power consumption increases, more heat is generated. This heat needs to be removed one way or another, further increasing costs.
In view of the foregoing, what are needed are apparatus and methods to reduce the power consumed by storage systems and other devices. Such apparatus and methods would ideally be able to power down certain storage devices in a storage system to conserve power. Further needed are apparatus and methods to migrate infrequently-accessed data to storage devices that are powered down. Likewise, apparatus and methods are needed to retrieve, or “surface,” data from powered-down storage devices when the data is needed.